Two color, shadow mask-type cathode ray tube

ABSTRACT

An improved aperture mask is provided for use in a two beam shadow mask type of color cathode ray tube. The mask is utilized in the formation and subsequent operation of a patterned screen including a repetitive array of two phosphor areas. The multitude of apertures defined by the interstitial webbing of the mask member are arrayed in a plurality of parallel rows having given directional orientations. Any three mutually adjacent apertures in any two adjacent parallel rows are oriented to form an isosceles right triangular relationship. The resultant screen associated therewith exhibits enhanced resolution and brightness.

United States Patent Say l 1March 13, 1973 TWO COLOR, SHADOW MASK-TYPE CATHODE RAY TUBE Donald L. Say, Seneca Falls, N.Y.

GTE Sylvania Incorporated, Seneca Falls, N.Y.

June 16, 1971 [75] lnventor:

Assignee:

[56] References Cited UNITED STATES PATENTS l/l952 Jenny ..3l3/85 S X l/l956 Grimm et al. ..313/92 B X i rsgel fm, go. a

leggy Primary Examiner-Robert Segal AttorneyNorman J. OMalley et al.

[57] ABSTRACT An improved aperture mask is provided for use in a two beam shadow mask type of color cathode ray tube. The mask is utilized in the formation and subsequent operation of a patterned screen including a repetitive array of two phosphor areas. The multitude of apertures defined by the interstitial webbing of the mask member are arrayed in a plurality of parallel rows having given directional orientations. Any three mutually adjacent apertures in any two adjacent parallel rows are oriented to form an isosceles right triangular relationship. The resultant screen associated therewith exhibits enhanced resolution and brightness.

4 Claims, 3 Drawing Figures PATENTEUMAR 1 3 I975 3,720,854

SHEEI 2 OF 2 mimmlh:

VENTO .DONA L. S

ATTORNEY TWO COLOR, SHADOW MASK-TYPE CATHODE RAY TUBE BACKGROUND OF THE INVENTION wherein specific data for comparative purposes is visually evidenced, it is desirous to present the various data factors in a vivid luminous manner. In some applications a limited number of simultaneous color or'hue differences are adequate for the presentation of an evaluation display. For this type of system, a so-called two color cathode ray tube is appropriate. Such a tube normally utilizes two electron beams and a patterned screen formed of a repetitive array of two separate phosphor areas-from which the additive aspects of a composite hue may also be obtained. A conventional shadow mask tri-color tube can be adapted for this usage by eliminating one of the three electron guns and the associated phosphor component in the screen pattern. However, when such is done, the blank areas in the screen are detractivefactors affecting both the resolution and the brightness of the display. Thus, it has been found that the aperture arrangement in the conventional tri-color shadow mask tube cannot be effectively utilized to produce an efficient two-phosphor screen of the quality required for the display application.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide an improved shadow mask for a cathode ray tube having an aperture array appropriate for effecting an efficient twophosphor patterned screen exhibiting enhanced resolution and improved brightness.

Another object is to provide an improved apertured shadow mask'and a two-phosphor screened panel combination for use in a two beam cathode ray tube.

A further object is to provide an improved two beam shadow mask cathode ray tube employing a discrete mask aperture array and an associated two phosphor patterned screen.

The foregoing objects are achievedin one aspect of the invention wherein an improved shadow mask, for use in a cathode ray tube employing two electron beams and a patterned screen including a repetitive array of two phosphor areas, exhibits a discrete aperture arrangement. The foraminous mask member comprises a multitude of apertures which are defined by the interstitial webbing and arrayed in a substantially uniform pattern effecting a plurality of parallel rows of given directional orientations. Any three mutually adjacent apertures in any two adjacent parallel rows are oriented in a related manner to form an isosceles right triangular relationship. The patterned screen formed and associated with the aperture array of this mask exhibits a luminescent display having markedly enhanced resolution and brightness.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged fragmentary plan view illustrating a prior art relationship of the mask apertures with the associated patterned screen;

FIG. 2 is a partial perspective view showing the screen, shadow mask and electron gun relationships of a tube embodying the invention; and

FIG. 3 is an enlarged fragnentary plan view illustrating the patterned screen and mask aperture relationship of the invention taken along the line 33 in FIG. 2 as viewed from the orientation of the source of the electron beams.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

The descriptive phraseology two-color cathode ray tube as used in this specification refers to a tube employing two separate electron beams and a patterned cathodoluminescent screen comprising a repetitive array of two phosphor areas. Each of the phosphor areas is made up of one or more phosphor materials which, when excited, emits a distinctive hue. Simultaneous excitation of both phosphor areas produces a third color fonned as an additive composite hue. By way of example, green G and red R luminescent dots will be described herein.

With reference to the drawings, there is shown in FIG. 1 an enlarged fragmentary plan view of a prior art aperture mask 11 and associated patterned screen 13 relationship as viewed from the source of electron beams within the tube. The foraminous shadow mask member 11 has therein a multitude of apertures 15 defined by the opaque interstitial webbing l7 and presents an aperture array as employed in a conventional tri-color or tri-dot color cathode ray tube. The aperture array is directly related to the X and Y axes of the mask and the diagonals associated therewith. For example, three adjacent apertures 15 in two adjacent parallel rows Y-Y' and G-G', having centers 1, m, and 0, form an equilateral triangle lmo wherein all three sides are of equal lengths and the included angles are 60, therefore &= &In considering adjacent parallel rows X-X' and E-E', the adjacent apertures having centers 0, m, and n form an isosceles triangle omn. While related triangles lmo and omn have a common side om and equal sides om and mn, they are otherwise respectively dissimilar: d) 60, while li= 60, whereas [Bl 30; and side I0 is shorter than side on. In view of the unlike triangular relationships, the linear spacings t between apertures in the rows'oriented in the Y-Y' direction are equal to the linear spacings between apertures in the rows oriented in the diagonal W-W and J-J' directions, while the aperture spacings w in the X-X' directional orientation are greater. In similar manner the color repeat spacings v between adjacent parallel rows of apertures in the Y axial direction are greater than the row spacings s in the X direction.

The two-color screen 13 formed on the glass substrate or receiving panel 19 and operationally associated with the prior art mask 11 is comprised of pairs of GandRphosphor areas. Since the third phosphor color area hasbeen eliminated from this twocolor screen 13, the panel area 21 usually covered by the third phosphor is free of phosphor material in the screen pattern 13 shown. Thus, it is clearly evident that high resolution and brightness cannot be expected from the aforedescribed prior art screen 13 wherein over one-third of the panel screen area is free of phosphor material.

In reference to FIG. 2, a partial perspective view denotes portions of a cathode ray tube 25 enclosed by a fragmentarily shown envelope 27 wherein the viewing panel 19 has a two-color screen pattern 29 in the form of repetitive pairs of contrasting phosphor areas disposed in rows thereon. A metallic foraminous shadow mask 31 is spatially positioned relative to the screen 29 being directly associated with the formation and subsequent operation of the patterned screen. In usage, the apertured shadow mask 31 and screened viewing panel 19 are considered as a combination assembly 33, and as such are conventionally spatially affixed by means not shown. Additionally, predeterminately positioned within the envelope 27 is a source of electrons 37 oriented in a manner to direct two separate electron beams 39 and 41 toward the apertured shadow mask 31 and the related screen 29. As shown, the electron beams 39 and 41 converge at the mask 31 passing through an aperture 43 therein and thence selectively impinging and exciting separate phosphor areas of the screen 29 to provide a luminescent display.

In greater detail, reference is made to FIGS. 2 and 3 wherein the shadow mask 31 comprises a multitude of apertures 43 defined by the opaque interstitial webbing 45. The apertures are arrayed in a substantially uniform pattern being adjacently related in a manner to effect a plurality of rows which, in turn, define a plurality of linear directional relationships such as, C-C', Y-Y, LL' and K-K. The rows of a given directional orientation are substantially parallel, as for example: X-X' and A-A, Y-Y' and C-C', L-L' and M-M, and K-K' and N-N. The rows X-X' and Y-Y' define the respective X and Y axial directions in the shadow mask member Any three mutually adjacent apertures in any two adjacent parallel rows are substantially oriented in an isosceles right triangular relationship. For example, three mutually adjacent apertures, having centers of a", b, and c respectively, are oriented in adjacent parallel rows Y-Y' and C-C', in O-O and L-L', and in N-N and K-K'. The resultant triangle abc includes a right angle Land an acute angle &of 45. Since the acute angles are complements of each other, the remaining acute angle @is also 45, and therefore the respective sides ab and ob arevequal; consequently, the spacings p and q between adjacent diagonal rows are also equal. A similar isosceles right triangle cbd is formed of the three mutually adjacent apertures 43 having centers c, b", and d which are oriented in adjacent parallel rows X-X' and A-A, in L-L and M-M', and in N-N' and K-K'. The two isosceles right triangles abc" and cbd" are equal since they have a common side cb and angular equalities, i.e. 40F 40= e' LE (8. The hypotenuse ac" of triangle abc is definitive of the Y axial direction in the mask, and the counterpart hypotenuse cd of triangle cbd is defnitive of the X axial direction. In each of the respective triangles abc and cbd, the sides forming the right angle, for example, in abc, sides ab" and ob forming the right angle @define the diagonal directions N-N and L-L in the mask, each diagonal being associated with the respective X and Y axes in substantially 45 angular relationships. The described diagonal relationships diametrically divide each of the apertures 43 into four substantially equal 90 segments 49, 50, 51 and 52.

The linear spacings h and f between the individual mask apertures in the rows directionally associated with both the X and Y axes are substantially equal since the hypotenusal sides ac and cd of similar triangles abc" and cbd are of equal lengths. The spacings e and g between adjacent parallel rows, of apertures, such as X-X', A-A and Y-Y' and C-C', in both the X and Y directions are equal in view of the equalities of dimensions bj and bj', each being normal to the mid-points of the hypotenusal sides ac and cd of the similar triangles abc and cbd. Therefore, the spacings e and g between adjacent parallel rows of apertures, which are in effect color repeat dimensions, associated with both the X and Y axial directions are advantageously equal; and in addition, these spacings e and g are equal to sub stantially one-half the respective linear spacings f and h between the apertures in the respective rows in view of the equalities the aforementioned triangular dimensions whereof, aj' jc =cj'= j'd.

The improved shadow mask 31 of the invention has more apertures per area or greater transparency than does the described prior art mask 11, and therefore the improved mask 31 affords higher resolution and enhanced brightness by permitting the passage of a greater density of exciting electrons. In considering the greater transparency of the improved mask 31, attention is drawn to FIG. 3 wherein the aforedescribed triangular area abc is referenced. For purposes of example, the following values are ascribed:

Aperture dia. k 0.0090 inch ac orf 0.0250 inch jb or g (same asjb or e) 0.0125 inch color repeat spacing for both X and Y axes /2 area of aperture Improved mask transparence area of triangle abc Improved mask color repetitions per inch 1 vertically and horizontally 0125 repeats/in.

Prior art mask transparency= Prior art mask color repetitions per inch vertically l/0.0l08 92.5 repeats/in. Prior art mask color repetitions per inch horizontally l/0.0188 53.2 repeats/in. Thus, on the basis of comparative dimensions, the mask 31 of the invention provides improved transparency and resolution for two-color tube utilization.

With reference to FIGS. 2 and 3, the two-color screen pattern 29 comprises a repetitive array of two phosphor areas or dots which are substantially equally adjacent to one another, being disposed in accordance with the aperture array of the mask 31. The two phosphor areas, in this instance, are conventional cathodoluminescent materials such as those that emit green G or red R luminous hues when electron excited. The two phosphor areas,G,R are alternately and adjacently disposed in substantially linear parallel rows in both horizontal and vertical X and Y, directional relationships in the screen 29. In the X axis directional relationship, the phosphor rows are oriented in a manner that the linear diametrical axes of the phosphor dots 2-2 and that of the apertures X-X' are'substantially coincidental. Each pair of contrasting phosphor areas is related to a respective aperture in the mask in a manner that the center of the aperture is substantially superposed over the region of adjacency between the two contrasting areas of the pair. By way of example in FIG. 3, the center of aperture 43 is superposed over the region of adjacency of contrasting areas G and R in the horizontal row X-X. There are no large vacant areas 21 in the screen as are evidenced in the-prior art screen 13 in FIG. 1.

I As shown, the phosphor areas G,R have a diameter i which is greater than the diameter k of the related aperture. Such diametrical relationship is not intended to be limiting, as the dots may also be of a size equal to or smaller than the apertures and still be in keeping with the concept of the invention. There may be instances when it is desirous to form a screen pattern array wherein the individual phosphor areas are disposed in an equidistant spaced-apart relationship.

Such alteration of the pattern spacing could necessitate a proportional modification of the triangular dimensions between the apertures in the mask, however, the dimensional relationships therebetween would remain substantially constant in keeping with the teaching of the invention.

' In FIG. 2, the source of electrons 37 is an electron gun structure assembled in a manner to provide and direct two separate electron beams 39, 41 to the maskscreen portion 33 of the tube 25. The individual beams are controlled to selectively excite a respective one of the two phosphor areas G,R in a predetermined sequence to provide a luminescent display in the twocolor screen 29. As indicated, the directional line of scan 8-8 of the two beams 39, 41 is substantially parallel with the X-X' axial orientation of the mask apertures 43 and such is preferred; but there may be occasions when the electron beams are oriented to scan the mask 31 and associated screen 29 in a modified manner. It has been found that the line of scan S-S can be shifted clockwise or counter-clockwise with reference to the X-X' of the mask, but such deviation should not exceed a substantially 45 angular relationship with the X-X' axis of the mask.

Thus, there is provided cathode ray tube shadow mask having a discrete aperture array for effecting an efficient two-phosphor patterned screen for use in a two-beam tube whereof the resultant luminescent image exhibits enhanced resolution and improved brightness.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

I claim:

1. A color cathode ray tube having an enclosing envelope with a viewing area defined therein, said tube comprising:

a shadow mask structure positioned within said envelope in spaced adjacency to said envelope viewing area, said shadow mask being a metallic foraminous member wherein the interstitial webbing defines a multitude of apertures arrayed in a substantially uniform pattern, said apertures being substantially round and adjacently related to effect a plurality of rows defining a plurality of lateral directional X and Y and diagonal relationships, said rows of a given directional orientation being substantially parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being substantially oriented in an isosceles right triangular relationship;

a cathodoluminescent screen formed on the interior surface of the viewing area of said envelope adjacent to said mask, said screen being dot-patterned with a repetitive array of two substantially round contrasting phosphor areas emissive of different spectral emissions substantially equally adjacent to one another being disposed substantially contiguously as repetitive pairs in horizontal rows in accordance with the aperture array of said mask, each pair of contrasting phosphor areas being related to a respective mask aperture whereof the center of. the aperture is substantially superposed over the region of adjacency between the two contrasting areas of the pair; and

a source of electrons positioned within said envelope in a manner to direct two separate electron beams toward said envelope viewing area to scan and traverse the apertures in said mask in a manner related to the X axial direction thereacross and impinge the screen therebeyond, said beams selectively exciting the pattern array of the two differential phosphor areas in a predetermined sequence to provide a luminescent display.

2. A color cathode ray tube according to claim 1 wherein the isosceles right triangular relationships of said mask apertures are oriented in a manner that the hypotenusal sides of said triangles define the respective X and Y axial directions in said foraminous member, said screen having like axes, and wherein said electron beams are Oriented to scan the mask and associated screen in a manner substantially parallel with said X axes.

3. A color cathode ray tube according to claim 1 wherein the linear spacings between the mask apertures in the rows directionally associated with both the X and Y axes are substantially equal, and wherein the spacings between adjacent parallel rows of apertures in both the X and Y axes are equal, and wherein the spacings between adjacent parallel rows of apertures associated with both the X and Y axes are equal to substantially one-half the linear spacing between-the apertures in said rows directionally associated with both of with said respective axes in substantially 45 angular relationships, and wherein said electron beams are oriented to scan said mask and associated screen in a manner that the line of scan does not exceed a substantially 45 angular relationship with said X axis. 

1. A color cathode ray tube having an enclosing envelope with a viewing area defined therein, said tube comprising: a shadow mask structure positioned within said envelope in spaced adjacency to said envelope viewing area, said shadow mask being a metallic foraminous member wherein the interstitial webbing defines a multitude of apertures arrayed in a substantially uniform pattern, said apertures being substantially round and adjacently related to effect a plurality of rows defining a plurality of lateral directional X and Y and diagonal relationships, said rows of a given directional orientation being substantially parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being substantially oriented in an isosceles right triangular relationship; a cathodoluminescent screen formed on the interior surface of the viewing area of said envelope adjacent to said mask, said screen being dot-patterned with a repetitive array of two substantially round contrasting phosphor areas emissive of different spectral emissions substantially equally adjacent to one another being disposed substantially contiguously as repetitive pairs in horizontal rows in accordance with the aperture array of said mask, each pair of contrasting phosphor areas being related to a respective mask aperturE whereof the center of the aperture is substantially superposed over the region of adjacency between the two contrasting areas of the pair; and a source of electrons positioned within said envelope in a manner to direct two separate electron beams toward said envelope viewing area to scan and traverse the apertures in said mask in a manner related to the X axial direction thereacross and impinge the screen therebeyond, said beams selectively exciting the pattern array of the two differential phosphor areas in a predetermined sequence to provide a luminescent display.
 1. A color cathode ray tube having an enclosing envelope with a viewing area defined therein, said tube comprising: a shadow mask structure positioned within said envelope in spaced adjacency to said envelope viewing area, said shadow mask being a metallic foraminous member wherein the interstitial webbing defines a multitude of apertures arrayed in a substantially uniform pattern, said apertures being substantially round and adjacently related to effect a plurality of rows defining a plurality of lateral directional X and Y and diagonal relationships, said rows of a given directional orientation being substantially parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being substantially oriented in an isosceles right triangular relationship; a cathodoluminescent screen formed on the interior surface of the viewing area of said envelope adjacent to said mask, said screen being dot-patterned with a repetitive array of two substantially round contrasting phosphor areas emissive of different spectral emissions substantially equally adjacent to one another being disposed substantially contiguously as repetitive pairs in horizontal rows in accordance with the aperture array of said mask, each pair of contrasting phosphor areas being related to a respective mask aperturE whereof the center of the aperture is substantially superposed over the region of adjacency between the two contrasting areas of the pair; and a source of electrons positioned within said envelope in a manner to direct two separate electron beams toward said envelope viewing area to scan and traverse the apertures in said mask in a manner related to the X axial direction thereacross and impinge the screen therebeyond, said beams selectively exciting the pattern array of the two differential phosphor areas in a predetermined sequence to provide a luminescent display.
 2. A color cathode ray tube according to claim 1 wherein the isosceles right triangular relationships of said mask apertures are oriented in a manner that the hypotenusal sides of said triangles define the respective X and Y axial directions in said foraminous member, said screen having like axes, and wherein said electron beams are oriented to scan the mask and associated screen in a manner substantially parallel with said X axes.
 3. A color cathode ray tube according to claim 1 wherein the linear spacings between the mask apertures in the rows directionally associated with both the X and Y axes are substantially equal, and wherein the spacings between adjacent parallel rows of apertures in both the X and Y axes are equal, and wherein the spacings between adjacent parallel rows of apertures associated with both the X and Y axes are equal to substantially one-half the linear spacing between the apertures in said rows directionally associated with both of said axes. 